diff --git a/awx/main/models/inventory.py b/awx/main/models/inventory.py
index 38c8247b07..70b4dcaa9f 100644
--- a/awx/main/models/inventory.py
+++ b/awx/main/models/inventory.py
@@ -927,11 +927,12 @@ class InventorySourceOptions(BaseModel):
     source_vars_dict = VarsDictProperty('source_vars')
 
     def clean_instance_filters(self):
+        instance_filters = unicode(self.instance_filters or '')
         if self.source != 'ec2':
             return ''
         invalid_filters = []
         instance_filter_re = re.compile(r'^(?:tag:.+)|(?:[a-z][a-z\.-]*[a-z])=.*$')
-        for instance_filter in self.instance_filters.split(','):
+        for instance_filter in instance_filters.split(','):
             instance_filter = instance_filter.strip()
             if not instance_filter:
                 continue
@@ -941,16 +942,17 @@ class InventorySourceOptions(BaseModel):
             raise ValidationError('Invalid filter expression%s: %s' %
                                   ('' if len(invalid_filters) == 1 else 's',
                                   ', '.join(invalid_filters)))
-        return self.instance_filters
+        return instance_filters
 
     def clean_group_by(self):
+        group_by = unicode(self.group_by or '')
         if self.source != 'ec2':
             return ''
         get_choices = getattr(self, 'get_%s_group_by_choices' % self.source)
         valid_choices = [x[0] for x in get_choices()]
         choice_transform = lambda x: x.strip().lower()
         valid_choices = [choice_transform(x) for x in valid_choices]
-        choices = [choice_transform(x) for x in self.group_by.split(',') if x.strip()]
+        choices = [choice_transform(x) for x in group_by.split(',') if x.strip()]
         invalid_choices = []
         for c in choices:
             if c not in valid_choices and c not in invalid_choices:
diff --git a/awx/main/tests/inventory.py b/awx/main/tests/inventory.py
index 1d9cb517e1..036246e0bd 100644
--- a/awx/main/tests/inventory.py
+++ b/awx/main/tests/inventory.py
@@ -1256,10 +1256,36 @@ class InventoryUpdatesTest(BaseTransactionTest):
             'source': 'ec2',
             'credential': aws_cred_id,
             'source_regions': '',
+            'instance_filters': '',
+            'group_by': '',
         }
         with self.current_user(self.super_django_user):
             response = self.put(inv_src_url1, inv_src_data, expect=200)
             self.assertEqual(response['source_regions'], '')
+        # Null for instance filters and group_by should be converted to empty
+        # string.
+        inv_src_data['instance_filters'] = None
+        inv_src_data['group_by'] = None
+        with self.current_user(self.super_django_user):
+            response = self.put(inv_src_url1, inv_src_data, expect=200)
+            self.assertEqual(response['instance_filters'], '')
+            self.assertEqual(response['group_by'], '')
+        # Invalid string for instance filters.
+        inv_src_data['instance_filters'] = 'tag-key_123=Name,'
+        with self.current_user(self.super_django_user):
+            response = self.put(inv_src_url1, inv_src_data, expect=400)
+        # Valid string for instance filters.
+        inv_src_data['instance_filters'] = 'tag-key=Name'
+        with self.current_user(self.super_django_user):
+            response = self.put(inv_src_url1, inv_src_data, expect=200)
+        # Invalid string for group_by.
+        inv_src_data['group_by'] = 'ec2_region,'
+        with self.current_user(self.super_django_user):
+            response = self.put(inv_src_url1, inv_src_data, expect=400)
+        # Valid string for group_by.
+        inv_src_data['group_by'] = 'region,key_pair,instance_type'
+        with self.current_user(self.super_django_user):
+            response = self.put(inv_src_url1, inv_src_data, expect=200)
         # All region.
         inv_src_data['source_regions'] = 'ALL'
         with self.current_user(self.super_django_user):
@@ -1293,6 +1319,8 @@ class InventoryUpdatesTest(BaseTransactionTest):
             'source': 'rax',
             'credential': rax_cred_id,
             'source_regions': '',
+            'instance_filters': None,
+            'group_by': None,
         }
         with self.current_user(self.super_django_user):
             response = self.put(inv_src_url2, inv_src_data, expect=200)